As school-aged children spend more time with friends and classmates away from the direct supervision of adults, they start needing to choose how they will behave (as opposed to simply complying with how caregivers want them to behave). At this point in time, they become strongly vulnerable to peer influence ("peer pressure") and to marketers who seek to convince them to make poor lifestyle choices in the hope in doing so they will win social acceptance and inclusion. For example, children can easily become overwhelmed by direct and indirect messages appearing in media and from peers about the desirability of cigarettes, alcohol, various drugs, promiscuous sex, and other risky behaviors. In order to inoculate children against this sort of pressure, parents and other caregivers need to talk directly, honestly and concretely in a plainspoken manner, without dramatic exaggeration or scare tactics, about the health dangers associated with smoking, drugs, alcohol, unprotected sex (and sex outside the context of a committed relationship in general), and other medically and emotionally risky behaviors. The point of such conversations is not to frighten children into doing what they "should" do, but rather to equip them with the facts so they can make independent and informed decisions. As children come to appreciate why certain course of action are self-defeating, many of them (not all) will tend to avoid engaging in those actions.
Though teaching children to think critically for themselves is the ultimate goal, many children will not be in a position to make the right decisions on their own at first, and thus it is practical to also offer children clearly verbalized expectations for how they need to behave and a description of the consequences that will occur if they make wrong choices. These expectations and consequences are offered as a sort of safety net. It is best if children are helped to make the right decision on their own. However, should they "fall" and succumb to negative peer pressure, the expectations and consequences will "catch" them so that they don't get hurt too badly.
For example, Mom should make it clearly known that she cares so much about keeping Lamar's lungs clean and healthy that she will punish him by revoking his privilege to play outside with friends for a week if she ever catches him smoking, carrying cigarettes, or even smelling like cigarettes. Even though he'll never admit it, Lamar will feel at his safest, most valued, and most centered when he has been given firm boundaries guiding his behavior that he violates at his peril. Setting clear boundaries and explicit, simple and easy to understand house rules are important methods for preventing misbehavior from occurring in the first place.
In order to be effective, the punishing consequence Mom selects to back up this set of expectations needs to be something she knows that Lamar will personally find aversive and naturally want to avoid. It won't work if Mom would not like that punishment but Lamar isn't too bothered by it. For instance, Mom should not threaten to remove Lamar's television watching privileges if Lamar doesn't really care about watching television all that much.
As children grow older, more mature and more capable, parental expectations of children's behavior need to be revised periodically so as to remain current. For example, rules governing how/when/where children are allowed to play with their friends need to be modified as children grow to accommodate their advancing independence and social capability. Some rule revisions will simply be reiterations of previous guidelines with expanded expectations, such as parents expecting their children to take on new chores as they become more capable. Some rules should remain unchanged, however, such as the one that says, "Treat family members and friends with respect and never use violence." Parents need to make sure that the rules they set are managed and adjusted so as to keep pace with their children's changing abilities and situations, at no time becoming too demanding or restrictive, while also never failing to support good healthy outcomes.
Almost all children will have friends whose parents are overly permissive and fail to reign in their behavior. When this happens, children will frequently notice that their friends get to do things that they are not allowed to do and see this as a fundamentally unfair situation. They may express this sense of discontent by whining something along the lines of, "But, MO-OM, Jimmy gets to stay up late! Why can't I? NO Faaaaiiir!"
In calling attention to the discrepancy between what the friend is allowed to do and what the child is allowed to do, the child is inviting the parents to participate in a power struggle or negotiation. It is usually a mistake for parents to enter a power struggle with their kids, however. In such cases, parents are often best served by simply explaining the rationale for why the house rules are the way they are, acknowledge that different families make different rules for different reasons, and stress that in this house, the rules are in place for safety and health reasons. It's okay for parents to think about modifying the rules when children demonstrate to them that they have matured and require an adjustment of the old rules to reflect their new capabilities (e.g., by calmly and logically requesting new privileges or opportunities). However, children who demonstrate the opposite (e.g., by whining) are not served by seeing their efforts at parental manipulation succeed.